1. Field of the Invention
The invention relates to fabric softening particles suitable for incorporation into detergent powders and a process for preparation of the particles.
2. The Prior Art
Traditionally, fabric softeners in liquid form have separately been added to the wash during the rinse cycle of automatic laundry washing machines. Consumers, however, desire the convenience of single step, single package products. In response, powdered detergents have been developed which incorporate fabric softening components. These formulations in addition to cleaning, soften laundry during the wash cycle. Unfortunately, organic cationic quaternary ammonium salts, the compounds normally used as softening agents, interact adversely with anionic surfactants found in detergent powders. The art has found various means to surmount this problem. One approach has been to substitute the cationic materials with clays capable of softening. Alternatively, organic cationic salts may be utilized when formulated in a manner which separates them from interaction with the deactivating anionic surfactants. A number of patents have combined both approaches. These patents report mixtures of both clay and a protected organic cationic quaternary ammonium salt.
GB 2,141,152A (Ramachandran) discloses a softening composition comprising discrete particles of a smectite-type clay and a detergent surface active agent in the ratio of at least 15:1. An organic cationic salt is then deposited onto the particles and adsorbed into the particle surface. In U.S. Pat. No. 3,936,537 (Baskerville et al.) discrete particles of a fabric softening additive are formulated by combining cationic quaternary ammonium salts with a dispersion inhibitor in the range of 4:1 to 1:4. These particles, called prills, may then be mixed with a granular detergent one of whose components may be a clay. Softening is further improved by the presence of the clay, especially by a mineral called bentonite. Dispersion inhibitors include waxes, polyhydric alcohols, aliphatic carboxylic acids, their esters or alcohols and alkoxylated condensates of the foregoing.
Further refinements of the cationic/dispersion inhibitor prills are described in U.S. Pat. No. 4,141,841 (McDanald). Therein the aforedescribed prills are agglomerated with a builder salt and an organic agglomerating agent to form large granules. Unlike the smaller prills, these particles because of their large size do not separate from the granular detergent mixture. Agglomeration is also an improvement over encapsulation because fabric-softening effectiveness remains high while still preventing inactivation by anionic surfactant.
In U.S. Pat. No. 3,862,058 (Nirschl et al.) and in U.S. Pat. No. 3,886,075 (Bernardino) clay is initially admixed in a crutcher with the detergent, builder and adjunct laundering ingredients. The resulting mixture is then spray-dried to form granules. Quaternary ammonium salt is sprayed onto these granules from a melt. This method of preparation was said to avoid affixing the quaternary salt to the surface of the clay by an ion-exchange mechanism.
By contrast with disclosures found in the foregoing patents, U.S. Pat. No. 3,948,790 (Speakman) reports that the replacement of exchangeable metal ions of clays with certain types of alkylsubstituted ammonium ions results in a material having softening effectiveness. Good performance was found limited to alkyl-substituted ammonium ions of total carbon atom content not exceeding 8.
It has also been well known that quaternary ammonium ion-exchanged organophilic clays are useful in the processing of textiles. For instance, U.S. Pat. No. 2,805,993 (Barnard et al.) discloses the lubricating properties of Bentone 34.RTM., a bentonite whose sodium ions are replaced with dimethyl dioctadecylammonium ions, sold by N.L. Industries, Inc.
From the foregoing review of the art, it is clear that the manner in which one combines quaternary ammonium salts, clays and/or quaternary ammonium ion substituted clays, will have a significant bearing upon fabric softening properties. Some beneficial combinations have been uncovered. It is evident, however, that the optimum combination of these "softener building blocks" has yet to be reported.
An object of this invention is to provide a fabric softening agent more efficient than heretofore known.
A further object of this invention is to provide a fabric softening agent that is compatible with anionic surfactants, does not yellow laundry and does not interfere with detergency or sudsing.
A final object of this invention is to provide detergent compositions incorporating the aforementioned improved fabric softening agent.